In the processing and packaging of semiconductor devices, wire bonding continues to be a primary method of providing electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). To form wire loops to provide this interconnection, bonding tools (e.g., capillary tools used during ball bonding, wedge tools used in wedge bonding) are used to press a wire against a bonding location using ultrasonic, thermosonic, or thermocompressive energy.
In the assembly of certain devices (e.g., power semiconductor devices) ribbon bonding may be used to provide electrical interconnection between locations. For example, U.S. Patent Application Publication Nos. 2006/0163315 (entitled Ribbon Bonding Tool and Process) and 2007/0141755 (entitled Ribbon Bonding in an Electronic Package) relate to ribbon bonding and are incorporated herein by reference.
Various of the drawings disclosed herein (e.g., FIGS. 1, 2, and 3A-3F) are useful in explaining conventional ribbon bonding tools and systems, as well as ribbon bonding tools and systems according to the present invention. FIG. 1 illustrates semiconductor die 110 supported by substrate 108 (e.g., leadframe 108). It is desired to provide a conductive interconnection between a location(s) on semiconductor die 110 (e.g., a die pad) and lead 108a of leadframe 108. Ribbon loop 112 provides such interconnection and includes first bond 112a and second bond 112b (both bonded to portions of semiconductor die 110), as well a third bond 112c on lead 108. Ribbon loop 112 is formed using ribbon bonding system 100 (e.g., a ribbon bonding machine). As is understood by those skilled in the art, a ribbon bonding system includes many conventional components and subsystems such as a material handling system, a vision system, a computer, and many others. However, for simplicity, only a few elements of ribbon bonding system 100 are shown. Such elements include ribbon bonding tool 102, ribbon guide 104, and cutting tool 106. During formation of ribbon loops (such as ribbon loop 112) a ribbon material is fed to ribbon bonding tool 102 from a ribbon supply (not shown) using ribbon guide 104. Ribbon bonding uses energy (e.g., ultrasonic energy to form bonds), and then, after formation of a ribbon loop, cutter 106 may be used to at least partially cut through the ribbon material prior to separation of the ribbon loop from the ribbon supply.
FIG. 2 is a perspective view of ribbon bonding tool 102 engaged in aperture 114a of ultrasonic transducer 114, where ribbon bonding tool 102 is aligned in aperture 114a using flat surface side 102k (in this case, front side 102k). As is understood by those skilled in the art, transducer 114 causes a “scrubbing” motion at the tip portion 102a, and particular, to working surface 102b of ribbon bonding tool 102. FIGS. 3A-3F are various views of exemplary ribbon bonding tool 102. FIG. 3A is a front view of tool 102, FIG. 3B is a top view of tool 102 (illustrating flat surface side 102k), FIG. 3C is a bottom view illustrating working surface 102b, FIG. 3D is a detailed view of a portion of FIG. 3A illustrating front edge 102d of tip portion 102a adjacent working surface 102b, FIG. 3E is a side view of tool 102, and FIG. 3F is a detailed view of a portion of FIG. 3E illustrating side edge 102f1 of tip portion 102a adjacent working surface 102b. 
Certain ribbon bonding tools have features formed on the working surface such as those shown in U.S. Patent Application Publication No. 2006/0163315 entitled Ribbon Bonding Tool and Process. FIG. 4A is an exemplary tip portion 102a of a conventional ribbon bonding tool 102. Tip portion includes working surface 102b, front edge 102d, back edge 102e, side edge 102f1, and side edge 102f2. Working surface 102b defines protrusions 102b1 and recesses 102b2 (where the protrusions and recesses may be part of a waffle or grid pattern on the working surface), where recesses 102b2 are between protrusions 102b1. A typical scrubbing motion of a ribbon bonding tool is from front to back, along the direction of the ribbon. In FIG. 4A, the scrubbing would typically occur in direction “d” which extends in a direction from front edge 102d to back edge 102e. 
FIG. 4B is a perspective view of a portion of ribbon loop 112 including first bond 112a bonded to bonding location 110. First bond 112a is formed using a “waffle” type ribbon bonding tool (similar to that shown in FIG. 4A) which forms openings/recesses 112a2 between protrusions 112a1. Unfortunately, conventional waffle style ribbon bond tools suffer from a number of deficiencies. For example, the edges of the protrusions on the working surface of the ribbon bonding tool tend to leave an irregular edge in the heel region of the ribbon bond, which may initiate cracks 112a3 at some point during the life of the ribbon bond. Other limitations of existing ribbon bonding tools relate to ribbon looping difficulties, amongst others.
Thus, it would be desirable to provide improved ribbon bonding tools.